Conventional techniques to extract a group that holds conversation (hereinafter, referred to as “conversation group”) from a plurality of speakers have been proposed for the purpose of directivity control used in hearing aids and teleconferencing apparatuses (for example, see PTL 1).
The technique described in PTL 1 (hereinafter, referred to as “conventional technique”) is based on a phenomenon that sound periods are alternately detected from two speakers in conversation. Under this assumption, the conventional technique calculates the degree of established conversation between two speakers on the basis of whether sound and silent periods alternate.
Specifically, the conventional technique raises the degree of established conversation if one of the two speakers gives sound and the other is silent for each unit time period; on the other hand, the technique lowers the degree if both speakers give sound or are silent for each unit time period. The conventional technique then determines the established conversation between those two speakers if the resultant degree in determination time periods is equal to or greater than a threshold.
This conventional technique allows two persons in conversation to be extracted from a plurality of speakers.